Cyclic polymers and catenanes by atom transfer radical polymerization (ATRP)

Abstract

The topologically interesting structures of cyclic polymers, catenanes and other macrocycles are of much interest for their unique chemical and physical properties. However, it is a challenge to design synthetic routes that afford controlled ring structures and connectivity, which is why the practical applications of these materials have not been explored. This review describes the advantages and disadvantages of ring expansion and ring closure methods for preparing cyclic polymers. This review also aims to provide a concise overview of the recent techniques of cyclization specifically by ring closure reactions from polymers grown primarily by atom transfer radical polymerization (ATRP). The ring closure techniques covered here are atom transfer radical coupling (ATRC), copper-catalyzed Huisgen azide-alkyne cycloaddition, Diels-Alder cycloaddition and alkylation of carboxylate salts to form esters. Ring expansion and ring closure methods have also been used in the preparation of polymer catenanes. A combination of ATRP and ATRC has been applied to the synthesis of homopolymer and block copolymer catenanes using a supramolecular template with ATRP initiators.

The synthesis of cyclic polymers by olefin metathesis: Achievements and challenges

“…Since this initial report, ATRP has enabled the ring‐closing synthesis of many examples of cyclic polymers using an array of different monomers including higher order structures such as bicyclic and multicyclic polymers, “sunflower” polymers, mikto star polymers . A recent review has summarized the use of CuAAC in the synthesis of cyclic polymers …”

Synthesis of cationic star polymers by simplified electrochemically mediated ATRP

“…Atom transfer radical polymerization (ATRP) is proven to be one of the most versatile reversible deactivation radical polymerization (RDRP) methods that enables the preparation of polymers with controlled molecular weights (MWs), narrow molecular weight distributions (M w /M n , MWDs), and targeted degrees of polymerization (DP) [1][2][3][4][5][6][7][8][9][10][11][12][13]. The advent of low amount catalyst ATRP system, such as simplified electrochemically mediated ATRP (seATRP) [14] offers more environmentally friendly reaction conditions for the synthesis of polymers [15].…”

Hyperbranched Multicyclic Polymer Built from Tailored Multifunctional Monocyclic Prepolymer

“…The combination of atom transfer radical poly merization (ATRP) and coppercatalyzed azidealkyne cycloaddition (CuAAC) is a powerful tool in the ringclosure strategy, because the azide group is relatively easy to obtain by substitution reaction of the ter minal halogen atom of polymer obtained via ATRP, which can be used in further click reaction, and considerable successful constructions have been achieved in recent years by this means. [5,[14][15][16][17][18] Reversible addi tionfragmentation chain transfer (RAFT) polymerization also plays an important role in the synthesis of cyclic polymers. [19][20][21][22] A significant advantage of RAFT polymerization over other living radical polymerization (LRP) processes is that it is compatible with a very broad set of monomers, even functional monomers with different groups including acid, amino, and salt.…”

“…In unimolecular ring closure process, linear polymers couple intramolecularly to afford cyclic polymers, thus it is not limited by stoichiometric equivalent. The combination of atom transfer radical polymerization (ATRP) and copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) is a powerful tool in the ring‐closure strategy, because the azide group is relatively easy to obtain by substitution reaction of the terminal halogen atom of polymer obtained via ATRP, which can be used in further click reaction, and considerable successful constructions have been achieved in recent years by this means . Reversible addition‐fragmentation chain transfer (RAFT) polymerization also plays an important role in the synthesis of cyclic polymers .…”